Yep, that's correct - there should be a 2 hour window available to edit a post (excluding moderators). We had to introduce it a while ago as spammers were taking advantage of the edit feature and started editing posts at a later date to add links and so on.
The 2 hour window is normally enough to correct spelling noticed after posting, etc... but if there's anything important to edit (for example, correcting a broken link) then feel free to drop me a message with the update and I'll edit it manually
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